Augmented critical The Tarrasque will score a critical hit on an attack roll of 18-20.

Elder of Annihilation The Tarrasque ignores the damage resistances of other creatures.

Surefooted The Tarrasque has advantage on attacks that would knock it prone.

Trample When the Tarrasque enters any enemy's space for the first time on a turn, the enemy must succeed on a DC 19 Dexterity saving throw or take 24 (5d12+10) bludgeoning damage and be knocked prone.

Earthbound Aura Creatures with a fly speed within 1 mile of the Tarrasque have their fly speed reduced to 0. If a creature is in midair when it becomes affected by Earthbind Aura, it falls at a rate of 60 feet per round until it reaches the ground.

Reflective Carapace Any time the Tarrasque is targeted by a magic missile spell, a line spell, or a spell that requires a ranged attack roll, roll a d12. On a 1 to 10, the tarrasque is unaffected. On an 11 or 12, the tarrasque is unaffected, and the effect is reflected back at the caster as though it originated from the Tarrasque, turning the caster into the target.

Regeneration The Tarrasque will regenerate 100 hit points at the start of it's turn as long as it has 1 hit point left

Unkillable The Tarrasque, when reduced to 0 hit points will fall over and will get back up with half of it's maximum hit points after 2d12 +6 rounds. the only way to completely get rid of it, is to bring it down to -125 hit points and have two wish spells cast to wish it away many miles underground.

ACTIONS

Bite +20 to hit, reach 15 ft., one target. Hit: 38 (4d12 + 10) piercing damage.If the target is a creature, it is grappled (escape DC 20). Until this grapple ends, the target is restrained, and the tarrasque can't bite another target.

Swallow The Tarrasque makes one bite attack against a Large or smaller creature it is grappling. If the attack hits, the target takes the bite's damage, the target is swallowed, and the grapple ends. While swallowed, the creature is blinded and restrained, it has total cover against attacks and other effects outside the Tarrasque, and it takes 100 (16d8) acid damage at the start of each of the Tarrasque's turns.
If the Tarrasque takes 60 damage or more on a single turn from a creature inside it, the Tarrasque must succeed on a DC 20 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of the Tarrasque. If the Tarrasque dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 35 feet of movement, exiting prone.

Rock Throw The Tarrasque picks up a large chunk of the ground or a building and throws it. +20 to hit. Range 400/1000 ft., one target. Hit: 80 (6d12 +10) bludgeoning damage.

Frightful Presence Each creature of the Tarrasque's choice within 120 feet of it and aware of it must succeed on a DC 17 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, with disadvantage if the Tarrasque is within line of sight, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the Tarrasque's Frightful Presence for the next 24 hours.

Multi-attack The Tarrasque can use its Frightful Presence. It then makes five attacks: one with its bite, two with its claws, one with its horns, and one with its tail. It can use its Swallow instead of its bite. Alternatively, it makes three rock attacks.

Seismic Shock The Tarrasque Jumps 20 ft into the air and slams down onto the ground and all creatures and structures on the ground within 100 feet of the Tarrasque are affected as they would be by the earthquake spell (save DC 20. This Attack requires five rounds to recharge.).

LEGENDARY ACTIONS

The tarrasque can take 4 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The tarrasque regains spent legendary actions at the start of its turn.

Attack. The tarrasque makes one claw attack or tail attack.Move. The tarrasque moves up to half its speed.Chomp (Costs 2 Actions). The tarrasque makes one bite attack or uses its Swallow.

A 165 ft tall mass of flesh that looks like a melted Tarrasque. This Monstrosity of nature is almost as powerful as a god, and lives to kill everything that exists.